"Foggy Lake Mashu", "Clear Blue Lake Masshu", both of these occurrences have always attracted people to this mysterious lake

Lake Mashu is within Akan National Park. It represents eastern Hokkaido and is loved as "Foggy Lake Mashu." The mysteriousness of this lake attracts many to it.
The caldera lake that was birthed from the explosion of the Mashu Volcano has a circumference of 20km and an area of 19.2 km squared. It boasts both a height of 351m above sea level and a depth of 212m, so it is also the 5th deepest in Japan.
The water level remains fixed, though no water flows in or out of it from outside, and it is the pride of the lake that, though somewhat mysterious, it is the clearest in the world with no impurities. Its unique deep blue color is known as "Mashu Blue." And, depending on the weather, the color may subtly change and is sure to delight visitors every time they come.
The lake is hidden when there is fog but seeing the "Mashu Blue" visible during breaks in this fog will be an experience you won't forget.
According to statistics taken over a 10-year span in the tourist season from May to October there are 100 days of no fog, 50 days where it is sometimes foggy, and 25 days where it is foggy all day.
Whether you see Lake Mashu on a clear day, disappearing and reappearing through fog, or it's completely concealed by fog, either way you can enjoy the mysteriousness of this lake. Perhaps the best time is when you can experience both the fog where you can't see an inch in front of you and then all of a sudden it changes to a beautifully sunny day.

Lake Mashu is surrounded by 300-400 meter criffs with a angle of 45° and Mount Mashu (Kamui-nupuri)、which attracts you to the contrast between the steep criffs and the quiet lake. Kamui-nupuri means "God's mountain" in Ainu, having been worshipped among people.
A small round island called "Nakajima (Kamuishu)" flows on the center of the lake, and it's described as "mysterious lake's dimple". You can enjoy these magnificent scenery from 3 viewing platforms. Also, there is Mashu Hot Spring, the oldest hot spring in eastern Hokkaido, around Lake Mashu. Why don't you relax in the bath after enjoying the mysterious lake formed by a volcanic eruption?